1. Field of Invention
This invention relates in general to disk files and, in particular, to an improved arrangement for controlling the temperature within a hermetically sealed disk file enclosure.
2. Description of the Prior Art
The function of a disk file is to store data for use by a data processing system. Various disk file configurations are suggested in the prior art. In general, data is stored on a magnetic disk surface in concentric recording tracks, each of which is assigned a unique address. A magnetic transducer is positioned in recording relationship with a selected track in response to an address signal supplied to a suitable positioning system.
As the capacity of disk files has increased, the aspects of temperature control of the disk enclosure have become more important from a number of different standpoints. It is known, for example, that heat is generated by the disk rotating in the enclosure and that the amount of heat will depend on the size of a disk and its speed of rotation. Thus, if one desires to increase storage capacity by merely increasing the number of disks in the file, some adjustment must be made to the overall configuration to insure that (1) a safe temperature is not exceeded, and (2) the temperature will be somewhat constant throughout the enclosure. The need to limit the temperature in the disk enclosure to some safe value is based on the fact that certain components, for example, integrated circuits, are mounted in the disk enclosure and are adversely affected if their normal operating temperature is exceeded.
In most prior art files, air cooling of disk enclosures is employed which requires a suitable blower to circulate air through the enclosure to remove heat. When an open loop system using ambient air is employed, various filters are used to insure that particles or contaminates in the air are removed prior to entering the disk enclosure. The character of the filter depends to a large degree on the head to disk spacing that has been established for the disk file recording system. Since one way to increase storage capacity is to increase linear recording density, which, in turn, is dependent to a large degree on the spacing of the magnetic head relative to the disk surface, the filter should be capable of removing particles from the air that would upset the air bearing relationship that is established between the head and the disk surface. Current disk files employ head to disk spacing in the range of 10 to 30 micro-inches, requiring relatively dense filters to remove unwanted contamination. If the recording density along the track is to be increased by decreasing the head to disk spacing, then some consideration must also be given to filtering out contaminants in the air that would upset the air bearing relationship. This generally involves some change to the air flow and, hence, temperature control.
It will be appreciated that, in this connection, while increasing the air flow through the disk enclosure will remove any additional heat, the power to circulate that air is also increased while the life of the filter is decreased, requiring an earlier replacement. In addition, the heat that is normally removed from the file must be dealt with, especially if a number of disk drives are located in the same area. Since it is not uncommon in large data processing systems to have 50 or more files in one area, the total amount of heat being removed is substantial. Special air conditioning requirements are, therefore, normal in such installations.
It is further known to increase storage capacity by increasing track densities. Many current disk files have track densities approaching 800 tracks per inch. In this area of track density, thermal considerations are extremely important in files which employ track following servo systems along with comb type accessing mechanisms. In such systems, a servo transducer cooperates with a separate servo surface to position the transducer carriage at a selected track or cylinder of tracks. The tracks on different disk surfaces at the same address form the cylinder. It has been found that the position of a track in a cylinder may vary relative to its original cylindrical position due to thermal effects in the disk enclosure. This phenomena is referred to as thermal track shift and, in some situations, can result in a degree of misalignment of the transducers relative to the track to cause data errors. The phenomena is caused by an uneven temperature distribution in the disk enclosure which causes a warmer disk to expand more than a relatively cooler disk. The phenomena also exists when the file is initially powered on, when the temperature within the disk enclosure is changing from ambient to its normal operating temperature where all components have reached a stable condition. This warmup period is, of course, a disadvantage since it may take 15 minutes or more to stabilize the temperature of the components within the disk enclosure.
The amount of heat being dissipated by the file also limits the manner in which the files can be physically configured in any installation. Since ambient air is required for cooling, files must be spaced so that each file is capable of receiving the required amount of ambient air. The prior art has recognized that the heat generated by the rotating disk surface can be reduced if the disk enclosure is filled with a gas that is less dense than air. Such an arrangement implies a hermetically sealed disk enclosure such as is shown in applicant's copending application Ser. No. 219,794 filed Dec. 24, 1980 which issued as U.S. Pat. No. 4,367,503 and is assigned to the assignee of the present invention. When a gas such as helium is employed in place of air, the drive motor of the file and the actuator for positioning the heads must also be included within the disk enclosure. If the motor is outside of the disk enclosure, there is no practical way to seal the drive motor shaft as it passes through the container to the disk hub in order to rotate the disk. As a result, a new heat source, i.e., the windings of the motor, must be considered in determining the thermal characteristics of the hermetically sealed disk file.
However, while the advantage of a hermetically sealed disk enclosure employing a helium gas is somewhat diminished because of the heat generated by the motor windings and the heat generated by the windings of the transducer positioning system, the overall thermal characteristics of the file are still considerably improved.
A disk file which generates a minimum amount of heat and a disk file enclosure which permits removal of the heat in an efficient manner so that storage capacity of the file may be increased allowing an increase in the storage packaging density of the files is desirable and needed. The present invention fulfills such a need.